SPUG: exec question

I have a script which manages a bunch of other scripts. Basically it
kicks off a specific script depending on the situation it sees when it
runs.
I want it to kick off the script then exit without waiting around for the
other script to finish. I thought this would do it:
# code to decide what script to use
exec($script);
but the manager script doesn't exit when it does the exec. Any ideas?
Thanks,
Dan.
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